The present invention relates to a friction engagement device.
In a conventional automatic transmission of an automobile or the like, a predetermined rotary element of a planetary gear device is connected to an input shaft by a clutch or subjected to rotation restriction by a brake in order to achieve a desired shift speed.
In a clutch and a brake, a friction plate adhered on both the front and rear surface with a plurality of friction materials and a separator plate are pressed together such that relative rotation between a first member and a second member spline-fitted to the friction plate and separator plate, respectively, is restricted. To remove frictional heat generated during the period from contact between the friction materials and separator plate to total restriction of relative rotation, and to prevent wear on the friction materials, a plurality of lubricating oil grooves are provided radially between adjacent friction materials. Lubricating oil is supplied to the plurality of lubricating oil grooves through lubricating oil supply holes drilled in the first member.
Japanese Patent Application Publication No. JP-A-2000-145819 (pages 3 and 4, FIGS. 1, 2, and 3) describes an invention in which a plurality of lubricating oil supply holes 12 drilled into a hub 8 (first member) of a wet type multiplate clutch 20 and a plurality of through oil grooves 11 (lubricating oil grooves) provided radially in both the front and rear surfaces of a friction plate 7 spline-fitted to the hub 8 are caused to face each other to reduce drag torque generated as a result of the viscosity of the lubricating oil used in the wet type multiplate clutch 20.